Thus, It is known that tris(hydroxymethyl) phosphine and salts thereof (referred collectively herein as THP) are capable of solubilizing iron sulphide by forming a coloured water-soluble complex. THP based products, especially the sulphate salt (THPS), are commonly added to oil wells as biocides. THP based products are highly effective at controlling sulphate-reducing bacteria, whose activity may be responsible for the original formation of the iron sulphide deposits.
Phosphate rock is the main source of phosphorus for use in the manufacture of organic phosphorus compounds, and typically phosphate rock contains impurities such as arsenic. The arsenic content in phosphate rock varies geographically. At very low levels, typically less than 10 ppm in the phosphate ore, the presence of arsenic does not cause any processing problems or “end-use/application” problems with downstream formulated products. Depending upon the downstream processing, variable amounts of arsenic will be still be present in finished phosphorus compounds/products. However, higher levels of arsenic, in the original phosphate rock can be carried through downstream processing and, can result in product instability and discoloration and/or precipitation.
Chinese sourced phosphate rock which is becoming one of main sources of phosphorus ores, typically contains 20-60 ppm arsenic and, in many instances, this is sufficient to result in an unacceptable discoloration of aqueous solutions of phosphorus-containing and/or precipitation of a problematic red/brown solid comprising elemental arsenic or arsenic compounds which is both unsightly and commercially unacceptable. Such precipitates would block filters, accumulate in tanks and form sludge. A concentration by weight above 1 ppm, typically above 5 ppm and certainly above 15 ppm of arsenic in the phosphorus-containing compound aqueous composition can generate the above mentioned problems, knowing that such weight concentration can reach 50 ppm and even more.
Thus, there exists a constant need in having aqueous stabilized phosphorus-containing compounds, more particularly, compositions wherein the arsenic impurity has been eliminated or at least alleviated totally or in part.